There has been proposed a method for bonding a substrate material such as a semiconductor wafer to a support such as a glass substrate via a temporary fixing material and then performing processes such as back-grinding of the substrate material and formation of back electrodes. It is necessary that the temporary fixing material be able to temporarily fix the substrate material on the support during processing and that the substrate material be readily separated from the support after the processing. Two-layered or three-layered systems have been proposed for such a temporary fixing material in consideration of properties such as adhesiveness, peelability, and heat resistance thereof (see, for example, Patent Documents 1-3).
Patent Document 1 discloses a wafer processing laminate including a support, a temporary adhesive layer on the support, and a wafer laid on the temporary adhesive layer, the wafer having a circuit-forming front surface and a back surface to be processed. The temporary adhesive layer includes a first temporary bond layer, which is a non-reactive thermoplastic organosiloxane polymer layer (A) that is releasably bonded to the front surface of the wafer, and a second temporary bond layer, which is a thermosetting modified siloxane polymer layer (B) that is laid on the first temporary bond layer and that is releasably bonded to the support.